I think the situation is this

The araby cavalry gets a command order to attack artillery. So first, move one stand of cavalry to get into contact with one stand of artillery (center of base's cavalry to center base's artillery).
If they choose the left stand of artillery they get into contact corner to corner with the pikes. Did the charge stops and have to fight with pikes?
If they choose right stand of artillery they get into contact corner to corner with xbow. Did the charge stops, recieve 3 shots of volley and then get stucked and have to fight with Xbow?
Let's think they choose to move the first stand to artillery left base. Is this a incidental charge and bonus are lost?
Then the arab player has to move the second stand to maximize battle line. There are two options here:
Did they have to go to his initial target (artillery) and then get stucked with Xbow, suffer 3 arrow bolts?
or did they ignore the initial target (Artillery) and focus into pikes the actual charging unit?
Sorry for the long post and multi chooice questions.
If the answers of all my questions are YES, then the cavalry never reachs the artillery, in the charge.